Well, since my tazer circuit went ka-put on me, i needed another source of electronic ignition that i can get for a good price. So i bought a generic disposable camera and i ripped it apart to get the circuit. I also took off the metal things that hold in the AA battery and replaced it with a 9v connector. I put in a 9v battery and i got it to work, but the way i would get a spark is by touching the wires. I need to be able to make it spark without having the wires touch and im not sure on how to do that. Also, the 9v gets hot when it keeps charging. Would that be a problem?

Also, i need to know how i am gonna get a momentary switch in there so that it will spark when i press the switch.

Pictures and a possible video to come. Sorry its late here i cant get them now but tomorrow i will.

I believe a typical camera flash circuit discharges at around 300V. Because of this low voltage, there is no way to make it jump a gap without using an ignition coil to boost the voltage. The high current is what causes a spark when the wires touch and it removes some material in the process. So, to use a camera flash as an ignition, you will have to make the electrodes touch and you will have to replace them after awhile.
You'd be better off using a piezo sparker, or better yet, an electric bbq sparker (my personal favorite as stun guns are illegal in my country). However, depending on how far north you live, they may be currently hard to find due to winter rolling in and the bbq season coming to an end - I went to five Canadian Tires before I bought the last sparker in my city until spring.

There should be a super-HV wire coming off one of the transformers, it generally leads to the middle of the flash tube. Put this between the electrodes, and it should ionize the air, thus allowing a spark.

Like I said in the other thread though, just get a piezo. I really don't see the appeal of these things.

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"If at first you dont succeed, then skydiving is not for you" - Darwin Awards

The two main terminals need to be say 3mm apart and the third trigger wire (in a small loop round that 3mm gap here but a loop isn't required, just needs to be close) between them.

I was running that off one used AA battery and you can see the kind of recharge time it has, I was guessing from the whine of the circuit as to how charged it became before pushing the trigger button but the mic can't pick that up. It sounds like someone snapping their fingers in the clip but it's rather louder irl and the spark is a lot more vigorous than a piezo.

They work if you put the effort in but for less effort you can get sparks which will also work fine.

I had the same circuit as Hotwired...before i getting shocked by touching the terminals. I was K.O. for a few seconds. 3mm is the very most you're gonna get, but the high voltage wire does help ita lot. The sound is like mmh...an airsoft BB hitting a wall. very crisp, very sharp and pretty loud bright blue spark. (even ignites my wooden workshop lol)

There's another almost identical thread going on right now ... Oh well.

1. The 9V battery is not needed, indeed the circuit will probably work better with the 1.5V battery since a 1.5V will supply much more current than the 9V. If you want longer battery life, and quicker recharge times, just replace the AA (or AAA) battery with a single C or D battery.

2. Using 9V will not boost the maximum voltage the circuit will create. The max voltage is limited by the voltage rating of the two caps, typically 300 or 330V. Trying to charge the cap's to a higher voltage just makes'm leak voltage.

Hotwire's description of the "trigatron" is excellent. Its a fun device to fiddle with a makes a pretty respectable bang all by itself. If you use three pointy screws threaded into and a short piece of 2" PVC pipe the bang is even louder. This setup is a bit more stable than Hotwired's three arm jig (plus it's better insulated). As the tips of the screws get blown off you can reset the gap by just screwing the screws in a bit farther.

This can be used to ignite a spudgun but it is a pretty fiddly setup and requires frequent maintance.

You might be able to just use the HV from the photoflash board. (In the trigatron setup of Hotwired just drop one of the leads from the photocap. Which one to remove you'll have to figure out by trial-and-error. Move the HV trigger to the now unused photocap electrode and omit the looped electrode. Will it ignite propane+air? The energy in the trigger cap is probably pretty marginal for ignition (0.5mJ in the cap, takes 0.2~0.5mJ to ignite propane+air). Try holding a disposable butane lighter near the spark gap and see if the spark'll ignite the lighter.

Any kind of transformer should do the trick. As long as it can handle the current. Before I had a auto ignition coil I used a step down transformer (240v primary, 12v secondary) I would pump voltage through the low voltage side and this would put enough voltage to jump about 2mm (not much...) Please also note I was useing a 9v battery to the secondary. If you were to wire the camera flash into the secondary, either it would kill the transformer, or you would get a nice high voltage. Pull one of these transformers out of a plug pack (wall wart in US?).

0.5 mJ in a 330V 120 µF cap? E= 1/2 ( C x V^2) in joules...i have 6.5 joules...That is way more than needed.
I also tried something else. You can wire the two lead from your cap to the low voltage side of a charging transformer. (just remove the little redressing circuit) when you trigger the discharge, a nice arc will form between the two high voltage wires (if they do stand next to each other) .

Mine would make red-ish arcs...(took a transformer from and old microwave...arcs were 2" long. scary stuff! and remember, always wear gloves and glasses.

I don't think the the HV wire actually produces a spark. I've watched it many times dry firing and it doesn't create a flash at all.

On a similar note, I tried 3000v from the single wire coming off a mini plasma ball circuit and although it's enough to create small arcs of plasma into thin air and make flames bend out of its way it can't ignite a gas mix.

CpTn_lAw wrote:0.5 mJ in a 330V 120 µF cap? E= 1/2 ( C x V^2) in joules...i have 6.5 joules...That is way more than needed. I also tried something else. You can wire the two lead from your cap to the low voltage side of a charging transformer. (just remove the little redressing circuit) when you trigger the discharge, a nice arc will form between the two high voltage wires (if they do stand next to each other) .

Mine would make red-ish arcs...(took a transformer from and old microwave...arcs were 2" long. scary stuff! and remember, always wear gloves and glasses.

The photoboard has two cap's on it. The big ass cap is typically 120 MFD charged to about 300V and does indeed contain about 6.5 Joules. But the big-ass cap is not what ignites the flash tube and the 300V it contains won't spark all by itself. The HV to ignite the flash tube comes from a ~0.02 MFD cap charged to about 300V (uses the same charging circuit as the big-ass cap). The smaller cap is dumped into the second transformer (typicall about a 1:30 stepup transformer rated at 10KV on the output side). The energy in the ignition spark is (1/2)(0.02MFD)(300V)<sup>2</sup>=0.9mJ (ignoring any losses in the tigger transformer).

So yes, the big ass caps has a couple orders of magnitude more energy than is needed to ignite the fuel, but the little triggering cap's energy is marginal. To use the big-ass cap's energy you have to do a trigatron type setup with three electrodes (which is basically identical to how the flash bulb works). If you use just the triggering circuit (the ~10KV) then the energy is pretty marginal for igniting propane in air, which typically is said to require a half a millijoule or so.

If you dump the big-ass cap through a step-down transformer wired backwards, as you suggest, you can probably get a decent spark. A 120V to 5V transformer would give a 24:1 step-up when wired backwards to the 300V cap. That should give about 7KV on the output and most of the ~6J in the cap should end up in the output spark. Only problem is coming up with a switch that can handle the ~6J in the big-ass cap. Most switches will fry their contacts pretty quickly carrying that much power. Lets see, 6J disharged in say 1mS would be 6 killowatts. A typical 120VAC wall switch is a pretty sturdy switch rated for 120 VAC at 15 AMPS (or so) and will handle about 1.8 killowatts, roughly 1/3th the power the photocap will supply. A typical pushbutton switch handles much less power and will cook its contacts pretty fast in this kind of setup.

One challenge with using a step-down transformer in a step-up mode, where the output voltage is in the many KV range, is that the insulation and the seperation of the output leads (which were designed to be the transformer's inputs) is insufficient to handle the much higher voltages. Often you have to put a big glob of RTV silicon on the output leads of the transformer to keep'm from sparking at the transformer.